Tumble dryers generally comprise an external casing provided with a rotatable drum where the wetted clothes to be dried are placed.
The drying effect is obtained by a flow of heated air forced inside the drum so as to pass through the tumbling clothes. The heated air removes the moisture from the clothes and then the air with moisture, i.e. the exhausted air, is expelled from the drum.
In conventional clothes dryers the duration of the drying cycle is based on the detected moisture level of the clothes. To this purpose, dryers include a moisture (or humidity) sensor in order to obtain information about the actual humidity of the laundry during the drying cycle.
A moisture sensor belonging to the know technique is disclosed in document U.S. Pat. No. 5,940,986; this document discloses a sensor placed inside the drum which comes into contact with the tumbling clothes during the drum rotation.
The sensor comprises a pair of elongated electrodes facing the interior of the drum such that during the drying cycle the clothes periodically engage and bridge the electrodes one another. The sensor electrodes are connected to a dryer moisture sensing circuit. The electrical resistance (or inductance) measured between the electrodes is indicative of the moisture level of the clothes bridging the electrodes. A high electrical resistance between the electrodes is indicative that the clothes are dry. A low electrical resistance between the electrodes is indicative of wet clothes bridging the electrodes.
In order to properly face the interior of the drum and to promote the contact with clothes, the electrodes are positioned next to the exhausted air opening. For example, in U.S. Pat. No. 5,940,986 the electrodes are mounted on an exhaust vent cover, partially covering the exhaust air opening and secured to the bulkhead of the dryer by a pair of fasteners.
As such, the front bulkhead assembly cooperates with the exhaust vent cover and the exhaust duct to define a receptacle for a blade-type lint filter, preventing the passage of fluff towards the exhaust duct. The lint filter is inserted vertically downwardly into the receptacle, and has an enlarged flange or rim that rests upon the surfaces surrounding the exhaust air opening. Similar solutions are disclosed in EP 1 473 402 or in EP 2 458 075,wherein the electrodes are positioned on a support fastened next to the exhaust air opening into which a pocket-type lint filter can be inserted.
In order to have a proper maintenance of this kind of dryers, the lint filter should be periodically removed and cleaned and, occasionally, also the electrodes should be at least wiped.
Nevertheless, it can be problematic to make the lint filter quickly removable and, at the same time, having electrodes easily reachable by the hand of a person. In fact, the front bulkheads should be preferably compact and the space available for the lint filter and for the electrodes and the respective support is quite limited.
As a consequence, it could be relatively troublesome to place back the lint filter properly in the receptacle after it has been removed for cleaning purpose. If the lint filter is improperly positioned, exhausted air might flow directly in the outlet conduit, with a risk of deposition of fluff in areas and/or components which may worse the functionality of the dryer or even cause serious safety risks.
To this regard, EP 0 443 361,GB2318408 or EP 0 250 789 disclose dryers comprising devices capable of controlling a proper positioning of the lint filter.
Nevertheless, these solutions require a dedicated circuit in order to provide information about the position of the filter and, in general, a more complex design of the dryer.